Stent delivery and deployment method

ABSTRACT

A encapsulated stent device for implantation within the vascular system includes a balloon of a balloon catheter formed around and adhered to a wire-like stent so that the outer surface of the device is more regular for delivery through the vascular system without an exterior sheath. The encapsulation securely anchors the stent to the balloon and maintains a low profile for negotiation of tortuous and narrowed vessels. Encapsulation requires placement of the stent over the balloon, placement of a sheath over the stent on the balloon, heating and preferably pressurization of the balloon to cause it to expand around the stent within the sheath, and cooling while preferably maintaining pressure to cause the balloon to adhere to the stent and to set the shape of the expanded balloon. Retainers may be placed at the distal and/or proximal ends of the stent during the encapsulation process, or the balloon material may expand to form retainers. The balloon defines at least three folded wings for symmetrical expansion of the stent, and one or more connected or non-connected stents may be encapsulated depending upon the area to be treated.

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/326,023, filed on Oct. 19, 1994 abandoned.

FIELD OF THE INVENTION

This invention relates to medical implant devices. More specifically,the invention relates to a stent encapsulated by an expandable balloonfor delivery and deployment in narrowing coronary or peripheral vesselsin humans.

DESCRIPTION OF THE PRIOR ART

Cardiovascular disease, including atherosclerosis, is the leading causeof death in the U.S. The medical community has developed a number ofmethods and devices for treating coronary heart disease, some of whichare specifically designed to treat the complications resulting fromatherosclerosis and other forms of coronary arterial narrowing.

An important development for treating atherosclerosis and other forms ofcoronary narrowing is percutaneous transluminal coronary angioplasty,hereinafter referred to as "angioplasty" or "PTCA". The objective inangioplasty is to enlarge the lumen of the affected coronary artery byradial hydraulic expansion. The procedure is accomplished by inflating aballoon within the narrowed lumen of the coronary artery. Radialexpansion of the coronary artery occurs in several different dimensions,and is related to the nature of the plaque. Soft, fatty plaque depositsare flattened by the balloon, while hardened deposits are cracked andsplit to enlarge the lumen. The wall of the artery itself is alsostretched when the balloon is inflated.

Angioplasty is typically performed as follows: A thin walled hollowguiding catheter is introduced into the body via a relatively largevessel, such as the femoral artery in the groin area or the brachialartery in the arm. Once access to the femoral artery is achieved, ashort hollow sheath, or guiding catheter, is inserted to maintain apassageway during the procedure. The flexible guiding catheter mustnegotiate an approximately 180 degree turn through the aortic arch todescend into the aortic cusp where entry may be gained to either theleft or the right coronary artery, as desired.

After the guiding catheter is advanced to the area to be treated byangioplasty, a flexible guidewire is inserted into the guiding catheterthrough an expandable balloon (described infra) and advanced to the areato be treated. The guidewire is advanced across the lesion, or "wires"the lesion, in preparation for the advancement of a balloon catheterhaving an expandable balloon portion composed of polyethylene, polyvinylchloride, polyolefin, or other suitable substance, across the guidewire. Currently, most balloons utilize two folded wings wrapped aroundthe hollow catheter tube. The balloon catheter is placed into positionby sliding it along the guide wire. The use of the relatively rigidguide wire is necessary for steerability to advance the catheter throughthe narrowed lumen of the artery and to direct the balloon, which istypically quite flexible, across the lesion. Radiopaque markers in theballoon segment of the catheter facilitate positioning across thelesion. The balloon catheter is then inflated with contrast material topermit fluoroscopic viewing during treatment. The balloon is alternatelyinflated and deflated until the lumen of the artery is satisfactorilyenlarged.

Unfortunately, while the affected artery generally can be enlarged, insome instances the vessel restenoses chronically, or closes downacutely, negating the positive effect of the angioplasty procedure. Inthe past, such restenosis has frequently necessitated repeat PTCA oropen heart surgery. While such restenosis does not occur in the majorityof cases, it occurs frequently enough that such complications comprise asignificant percentage of the overall failures of the PTCA procedure,for example, twenty-five to thirty-five percent of such failures.

To lessen the risk of restenosis, various devices have been proposed formechanically keeping the affected vessel open after completion of theangioplasty procedure. Such mechanical endoprosthetic devices, which aregenerally referred to as stents, are typically inserted into the vessel,positioned across the lesion, and then expanded to keep the passagewayclear. Effectively, the stent overcomes the natural tendency of thevessel walls of some patients to close back down, thereby maintaining amore normal flow of blood through that vessel than would be possible ifthe stent were not in place.

Various types of stents have been proposed, including self-expandableand expandable stents, although to date none has proven completelysatisfactory. Expandable stents generally are conveyed to the area to betreated on balloon catheters or other expandable devices. For insertion,the stent is positioned in a compressed configuration along the deliverydevice, such as a balloon catheter defining a balloon with two foldedand wrapped wings, to make the stent diameter as small as possible.After the stent is positioned across the lesion, it is expanded by thedelivery device, causing the length of the stent to contract and thediameter to expand. Depending on the materials used in construction ofthe stent, the stent maintains the new shape either through mechanicalforce or otherwise.

One such expandable stent for delivery on a balloon catheter is thePalmaz stent (U.S. Pat. No. 4,733,665) which may be thought of as astainless steel cylinder having a number of slits in its circumference,resulting in a mesh when expanded. The stainless steel cylinder iscompressed onto the outside of a non-expanded balloon catheter whichincludes stent retainer rings at each end of the stent to help tomaintain the stent on the balloon. Also, it is advisable to place asheath over the compressed stent and balloon assembly to retain thestent on the balloon and to create an even outer surface on the assemblyfor negotiation through the narrowed vessels. Boneau U.S. Pat. No.5,292,331 provides a unitary wire-like stent structure configured toform a plurality of upper and lower axial peaks, and is delivered andexpanded in a similar manner.

Significant difficulties have been encountered with deployment of knownprior art stents, including difficulty in maintaining the stent on theballoon and in achieving symmetrical expansion of the stent whendeployed. Currently, some stent delivery systems retain the stent on thedelivery catheter by means of either (a) plastically deforming the stentso that it is crimped onto the balloon, or (b) having the stent exhibita small enough internal diameter to act as an interference fit with theoutside diameter of the balloon catheter. The disadvantage with thesemethods is that the limited amount of securement between the stent andthe balloon is not always adequate to insure that the stent willproperly stay in place while advancing the stent to and through thetarget lesion. Additionally, the outer surface of the delivery device isuneven because the stent generally extends outwardly beyond the balloonand may contact a narrowed vessel wall and be displaced while thecatheter negotiates a narrowed vessel. Most known expandable stentdelivery systems utilize a removable sheath system on the outside of thestent, with or without retainer rings, that is removed once the stent isat the delivery site. This method protects the stent and provides asmooth surface for easier passage through vessels, but the methodincreases the crossing profile of the delivery device thereby decreasingthe device's ability to track through narrowed and tortuous vasculature.This and other complications have resulted in a low level of acceptancefor such stents within the medical community, and to date stents havenot been accepted as a practical method for treating chronic restenosis.

A long felt need exists for a delivery and deployment method for stentswhich ensures positional stability of the stent during delivery withoutthe need for an external sheath, thereby substantially decreasing thecross sectional profile of the balloon delivery device, and ensuressymmetrical expansion of the stent at deployment.

SUMMARY OF THE INVENTION WITH OBJECTS

The stent delivery and deployment method of this invention provides afrozen-in balloon in intimate contact with, and/or surrounding, a stentto assure stent attachment to the balloon, i.e. excapsulation. Thismethod is especially valuable at the proximal and distal ends of thestent for delivery purposes because a smoother transition occurs betweenthe distal and proximal surfaces of the balloon catheter and the distaland proximal ends of the stent, and it also is effective alongsubstantially the entire length of the stent. The frozen-in balloon formis achieved by encapsulating the stent so that the balloon may expandpart way around the stent and adhere thereto. The preferred method ofencapsulating the stent and balloon includes the steps of compressingthe stent on the outside of the balloon, placing a sheath over thecompressed stent to prevent expansion, and exposing the sheathed stentand balloon to an elevated temperature while pressurizing the balloon.The elevated temperature and pressurization causes the balloon to expandfrom below the stent to fill at least some of the spaces between thestent and the sheath. Following expansion and exposure to an elevatedtemperature, the balloon and stent are cooled while maintaining pressurein the balloon, so that the balloon profile will be "frozen around"(formed and somewhat adhered to) the stent. Alternatively, heat withoutpressurization of the balloon may be sufficient for encapsulation whenthe compressive forces of the sheath against the stent, which is pressedagainst the heated balloon, enables encapsulation of the stent.

If desired, the encapsulated stent may include conventional retainers atthe proximal and/or distal end of the balloon. Such retainers may belocated on top of the balloon or within the balloon. Additionally, theballoon itself may be used to form one or more stent retainers duringencapsulation. In this aspect of the invention, a space is definedbetween the balloon and the sheath, proximal and/or distal to the stent,so that the balloon expands to occupy the space and form one or moreretainers during the encapsulation process. Retainers assist in deliveryby providing a smooth transition between the encapsulated stent and thecatheter surface.

The preferred balloon for the method described above defines multiple(three or more) folded and wrapped "wings" or radial extensions on aballoon delivery device to assure radially symmetrical stent expansionduring deployment. The preferred balloon utilizes four wings for aBoneau stent having four axial turns at each end, and the balloon lengthand number of wings may be tailored to the particular stent or stents tobe deployed. By utilizing more than two wings, more symmetrical stentdeployment and vessel coverage can be achieved. Symmetrical stentdeployment results in symmetrical expansion and support of the targetlesion thereby suggesting use of multiple folds for standard PTCAballoon catheters with or without stents.

The method of this invention may be used with most self-expanding andexpandable prior art stents, such as tubular slotted stents, andincluding connected stents, articulated stents, and multiple connectedor non-connected stents. It is preferred to use a stent apparatus suchas the Boneau stent which is formed preferably from a single piece ofwire defining axial bends or turns between straight segments. The stentapparatus can then be encapsulated on a balloon catheter using theinventive method, delivered to the affected vessel and expanded inplace, all as described herein. Some of the intended uses include PTCAtype stenting, PTA type stenting, graft support, graft delivery, INRuse, GI tract use, drug delivery, and biliary stenting.

A general object of the present invention is to provide a stent deliveryand deployment method that overcomes the drawbacks and limitations ofthe prior art.

A specific object of the present invention is to provide a stentdelivery and deployment method that eliminates the need for a deploymentsheath and results in a low profile device with a more regular outersurface that may be delivered through tortuous, narrowed vessel.

Another specific object of the present invention is to provide a stentdelivery and deployment method which encapsulates the balloon and stentthereby securing the stent to the balloon and decreasing the profile ofthe stent and balloon.

Yet another specific object of the present invention is to provide astent delivery and deployment method which includes a balloon with threeor more wrapped and folded wings to ensure symmetrical deployment of thestent and expansion of the lesion to be treated.

One more specific object of the present invention is to provide anencapsulated stent and balloon have a retainer at the distal and/orproximal ends of the stent for maintaining the stent on the balloon andfor forming a smooth outer surface on the encapsulated stent device.

Still another specific object of the invention is to provide a methodfor encapsulating the majority of expandable and self-expanding stentsfor treating vessels in humans.

These and other objects, advantages and features of the presentinvention will become more apparent upon considering the followingdetailed description of preferred embodiments, presented in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross sectional view of two encapsulated stentsand a balloon embodying the principles of the present invention andshown on a balloon catheter device.

FIG. 2 is a longitudinal cross sectional view of the stents of FIG. 1compressed upon a balloon of a balloon catheter and shown prior to theencapsulation process.

FIG. 3 is a longitudinal cross sectional view of the stents and balloonduring the encapsulation process and shown positioned within interiorand exterior sheaths.

FIG. 4 is a cross sectional view taken along lines 4--4 of FIG. 2 andshowing four folded and wrapped wings of the balloon beneath one of thestents.

FIG. 5 is a cross sectional view showing the partially inflated form ofthe balloon around the stent.

FIG. 6 is a cross sectional view taken along lines 6--6 of FIG. 1 andshowing the frozen-in form of the balloon around the stent.

FIG. 7 is a longitudinal cross sectional view of two encapsulated stentsand a balloon showing retainers on the outside of the balloon.

FIG. 8 is a longitudinal cross sectional view of encapsulated stents anda balloon showing retainers on the inside of the balloon and attached tothe balloon catheter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an encapsulated stent assembly 20 embodying the principlesof the present invention. Two stent segments 10 are shown, and it willbe recognized by those skilled in the art that one or more stentsegments 10 may be used depending upon the size and configuration of thenarrowed vessel to be treated. Additionally, when more than one stentsegment 10 is used, the segments may be connected together byarticulated or rigid joints, or multiple single stent segments may bedeployed on the balloon catheter 30.

The balloon catheter 30 preferably is of a low profile design defining atapered distal tip 32, and an inner lumen 34 for insertion of aconventional guide wire (not shown). Any conventional or modifiedballoon catheter device may be used, such as a PTCA balloon catheter,and it is preferred that the expandable balloon portion 36 be configuredon the catheter 30 so that the collapsed balloon defines three or morefolded wings 38 which are wrapped around the outside of the cathetertube 40 as best shown in FIG. 4. In the embodiment in FIG. 4, theballoon 36 defines four folds 38 wrapped around the catheter tube 40 ina clockwise direction.

The preferred balloon 36 is formed from a material such as polyethylene,polyethylene terephthalate (PET), or from nylon or the like. The lengthand diameter of the balloon may be selected to accommodate theparticular configuration of the stent to be encapsulated. The balloonmay be carried on any catheter, although PTCA low profile catheters andover the wire catheters are preferred. The wings of the balloon areformed by pulling the balloon catheter through a forming tool having agenerally cylindrical cross section and defining a terminal openingconfigured to produce the desired number of wings in the balloon. Forinstance, configuration of the terminal opening may include three orfour slits radiating outwardly from the end of the forming tool,depending upon the number of folds to be produced. As the ballooncatheter is pulled through the forming tool, the balloon is pushedthrough the configured terminal opening and exits having, for instance,three separate flutes. The balloon catheter bearing the fluted balloonportion then is pulled into a sheath, preferably a two part sheath madeof Teflon or other suitable materials, so that the flutes fold and wraparound the catheter in a clockwise direction to form a generally spiralconfiguration around the catheter. The sheath-balloon catheter assemblyis subjected to heat, preferably by placing the assembly in a heat setoven, to form a crease in substantially the length of each of the foldedflutes. The sheath also may be of unitary construction. Following heatsetting, the balloon 36 retains the creases formed in the wings anddefines a generally symmetrical, cylindrical cross section, as best seenin FIG. 4.

Referring now to FIGS. 1-5, the Boneau stent is shown for illustrationpurposes only, and Boneau U.S. Pat. No. 5,292,331 is hereby incorporatedby reference. Each of the stent segments 10 is preferably a short,single wire stent 10 having an expandable, generally cylindrical bodyportion defining an inside surface and an outside surface. In the stentsegments 10 shown, the single piece of wire is bent to form a pluralityof upper and lower axial turns 2. The plurality of upper turns 2 areconnected to the plurality of lower turns 2 by substantially straightsections 4. The axial turns 2 can be seen to permit the stent segment 10to be compressed or expanded over a wide range while still maintaining asignificant mechanical force, such as required to prevent a vessel fromrestenosis or recoiling.

The stent segments 10 are preferably constructed of implantablematerials having good mechanical strength, such as implantable qualitystainless steel wire. The outside of the stent segments may beselectively plated with platinum, or other implantable radiopaquesubstances, to provide improved visibility during fluoroscopy. Thecross-sectional shape of the finished stent segment 10 may be circular,ellipsoidal, rectangular, hexagonal, square, or other polygon, althoughat present it is believed that circular or ellipsoidal may bepreferable.

The minimum length of each stent segment 10, or the distance between theupper turns and lower turns 2, is determined in large measure by thesize of the vessel into which the stent 20 will be implanted.Additionally, each stent segment 10 may define N number of turns, Nbeing preferable between 2 and 10. In the stent segments 10 shown in thedrawings, the segments define four upper and four lower axial turns 2.The stent segments 10 may be connected together by articulated or rigidjoints, or they may be deployed in a multiple spaced apart,non-connected configuration. The implanted encapsulated stent assembly20 will preferably be of sufficient length as to maintain its axialorientation with the vessel without shifting under the hydraulics ofblood flow (or other fluid flow in different types of vessels), whilealso being long enough to extend across at least a significant portionof the affected area. At the same time, the encapsulated stent 20 shouldbe short enough as to not introduce unnecessarily large amounts ofmaterial as might cause undue thrombosis.

Following selection of the configuration and size of a stent segment 10,or multiple connected or non-connected stent segments, the segment orsegments 10 are compressed upon the outside of the balloon 36 of theballoon catheter 30 as best shown in FIGS. 2 and 4. An interior sheath42 is placed over each end of the balloon catheter 30, and an exteriorsheath 44 is placed over the interior sheath 42 to cover the stentsegments 10 and overlap with the interior sheath 42. The sheaths 42, 44are preferably non-expandable, and of a size to accept insertion of thestent segments 10 mounted on the balloon. Sheaths 42, 44 are shown forexample only, and it will be recognized by those skilled in the art thatthe balloon catheter and stents compressed thereon also may be placedwithin a mold to prevent expansion of the stent and configured to allowexpansion of the balloon as desired.

Next, the balloon catheter 30 preferably is pressurized by introducingair, or an inert gas such as nitrogen, through the lumen 34 into theinterior of the balloon to partially expand the balloon 36 within thesheaths 42, 44. The assembly then is exposed to an elevated temperaturewhile maintaining pressurization of the balloon. The pressure may be,for example, approximately 70 psi, and the elevated temperature may beachieved by placing the sheathed assembly into an oven at approximately150 degrees Fahrenheit to accomplish the heating step.

FIGS. 4-6 demonstrate, respectively, the configuration of the balloon 36prior to pressurization, the configuration during inflation, and thefrozen-in form configuration around and adhering to a stent segment 10.The balloon 36, and the wings 38, expand partially outwardly to occupyspaces around the axial turns 2 and between the straight sections 4 sothat the balloon 36 and the stent segments 10 are in intimate contact.Those skilled in the art will recognize that expansion of the balloonalso depends upon the form of the particular stent selected forencapsulation. Pressure between the stent and the balloon during heatingand balloon pressurization causes an adherence upon cooling. Adherenceis required for encapsulation which includes both intimate contactbetween the stent and the balloon as well as contact where the balloonsurrounds at least a portion of the stent.

Alternatively, pressurization of the balloon during the heating step isnot required where the sheaths 42, 44 fit tightly around thestent-balloon assembly. Pressure radiating inwardly from the sheaths 42,44 to press against the stents 10 causes the stents 10 to press againstthe heated balloon to achieve encapsulation.

Following heating, the balloon-stent assembly is removed from the heatand allowed to cool within the sheath. In those cases where the balloonhas been pressurized during heating, the internal pressure ismaintained. Cooling sets the shape of the balloon 36 which adheres tothe stent 10 following cooling, thereby allowing removal of the sheaths42, 44 for delivery of the assembly 20 within a vessel. Because of theadherence between the stent segment 10 and the balloon 36 of theencapsulated stent assembly 20 and the more regular surface area createdby encapsulating stent assembly segments, the encapsulated stentassembly 20 may be delivered without an external sheath.

As best shown in FIG. 3, and in FIG. 1, the encapsulated stent assembly20 may include a distal retainer 50 and/or a proximal retainer 52. Theretainers 50, 52 further secure the stent segment 10 to the balloon 36and create a smooth transition between the balloon/stent area of thedelivery device and the distal and proximal surfaces of the deliverydevice of the encapsulated stent assembly 20. The retainers 50, 52 maybe formed by the balloon itself during the encapsulation process, withthe configuration of the formed retainers 50, 52 determined by thedimensions of the spaces between the inner sheath 42 and the stentsegments 10. Formed retainers 50, 52 may be tapered or non-tapered.Alternatively, conventional retainers 54 may be attached over theballoon 36 prior to encapsulation, as shown in FIG. 7, or the retainers54 may be placed within the balloon 36, as shown in FIG. 8. One or tworetainers 54 may be used, and conventional retainers may be made fromany implantable material, such as implantable stainless steel orpolymers. Depending upon the configuration of the encapsulated stentassembly 20, retainers generally range in length from 0-20 mm.

The encapsulated stent assembly 20 is delivered to the desired site withor without a guiding catheter and using a conventional guidewire forsteerability to negotiate the area to be treated. Conventionalradiopaque markers and fluoroscopy may be used with the device forpositioning the encapsulated stent assembly and for viewing theexpansion procedure. Once the encapsulated stent assembly is in placeacross the lesion, the balloon may be inflated in a conventional manner.In the embodiment shown in FIGS. 4-6, the four wings 38 expand evenly toform four, symmetrical expanded flutes which symmetrically expand theinner diameter of the encapsulated stent outwardly by increasing theangle at the axial bends. During typical balloon expansion pressures ofapproximately 6 atmospheres or 90 psi, occurring within the human bodyand at body temperature, the heat set creases dissipate. The folded andwrapped wing configuration of the balloon ensures that the balloon willprovide radially uniform inflation so that the stent will expandsubstantially equally along each of the peaks. Uniform expansion of thelumen of the vessel occurs with uniform, symmetrical expansion of theencapsulated stent and balloon. The amount of inflation, andcommensurate amount of expansion of the stent, may be varied as dictatedby the lesion itself, making the stent assembly of the present inventionparticularly flexible in the treatment of chronic restenosis and abruptreclosure.

Because of the inflation of the balloon and expansion of the arterialwall of the vessel, the arterial wall bulges radially. At the same time,the plaque deposited within the intima of the vessel is displaced andthinned, and the stent is embedded in the plaque or other fibroticmaterial adhering to the intima of the vessel.

Following inflation of the balloon and expansion of the encapsulatedstent within the vessel, the balloon is deflated so that it pulls awayfrom the stent for removal. The deflated balloon generally forms from11/2 to 23/4 wings, including a generally U-shaped deflated form, andthe deflated wings do not retain the creases created by the heat settingballoon formation process discussed above. The deflated balloon easilyfolds around the balloon catheter for removal.

The exterior wall of the vessel attempts to return to its original shapethrough elastic recoil. The stent, however, remains in its expanded formwithin the vessel, and prevents further recoil and restenosis of thevessel. The stent maintains an open passageway through the vessel.Because of the low mass of the preferred support device of the presentinvention, thrombosis is less likely to occur. Ideally, the displacementof the plaque deposits and the implantation of the stent will result ina relatively smooth inside diameter of the vessel.

While the primary application for the stent is presently believed to betreatment of cardiovascular disease such as atherosclerosis or otherforms of coronary narrowing, the stent of the present invention may alsobe used for treatment of vessels in the kidney, leg, carotid, orelsewhere in the body. In such other vessels, the size of the stent mayneed to be adjusted to compensate for the differing sizes of the vesselto be treated.

While this invention has been described in connection with preferredembodiments thereof, it is obvious that modifications and changestherein may be made by those skilled in the art to which it pertainswithout departing from the spirit and scope of the invention. Forinstance, the encapsulation method and deployment is not limited to anyparticular expandable stent device. Accordingly, the aspects discussedherein are for illustration only and should not limit the scope of theinvention herein which is defined by the claims.

What is claimed is:
 1. An endovascular support device for implantationin a vessel within the human body comprising:at least one compressiblestent means mounted on a balloon of a balloon catheter; and wherein saidat least one compressible stent means is encapsulated by said balloon ofsaid balloon catheter.
 2. The endovascular support device of claim 1wherein the balloon is adhered to the compressible stent means whenencapsulated.
 3. The endovascular support device of claim 1 furthercomprising at least one retainer means for facilitating delivery of theencapsulated stent means for implantation.
 4. The endovascular supportdevice of claim 3 wherein the balloon forms the at least one retainermeans.
 5. The endovascular support device of claim 1 wherein the stentmeans comprises at least one expandable member bent to form a pluralityof substantially straight, non-overlapping sections connected by axialbends.
 6. A method for treating narrowing of vessels within humanscomprising the steps of:providing at least one endovascular supportdevice; mounting the at least one endovascular support device on aballoon of a balloon catheter; anchoring the at least one endovascularsupport device to the balloon by encapsulation of the at least oneendovascular support device by the balloon; advancing the ballooncatheter and the at least one encapsulated endovascular support deviceto an area to be treated within the vessels; inflating the balloon ofthe balloon catheter to expand the at least one encapsulatedendovascular support device within the area to be treated; and deflatingthe balloon of the balloon catheter so that the balloon pulls away fromthe at least one endovascular support device.
 7. A delivery system foran endovascular support device comprising:a balloon catheter having acatheter body and a balloon; means for selectively inflating anddeflating said balloon; at least one endovascular support device mountedon said balloon, said at least one endovascular support device having afirst diameter for intraluminal delivery and a second expanded diameterfor deployment in a vessel; wherein said balloon at least partiallysurrounds at least a portion of said at least one endovascular supportdevice thereby securing said at least one endovascular support device tosaid balloon for intraluminal delivery.
 8. The delivery system accordingto claim 7 wherein the at least one endovascular support device isretained in indentations formed in said balloon.
 9. The delivery systemaccording to claim 7 wherein the balloon adheres to the at least oneendovascular support device.
 10. The delivery system according to claim7 further comprising at least one retainer means for facilitatingdelivery of said at least one endovascular support device to apredetermined location within a vessel.
 11. The delivery systemaccording to claim 10 wherein the balloon forms the at least oneretainer means.
 12. The delivery system according to claim 7 wherein theat least one endovascular support means comprises at least oneexpandable member in the form of a plurality of substantially straightsegments connected by axial bends.
 13. The delivery system according toclaim 12 wherein said at least one expandable member is mounted ontosaid balloon to have an interior diameter D_(i) and wherein portions ofsaid balloon protrude through said substantially straight segments tohave a diameter greater than D_(i).
 14. A method for treating narrowingof vessels within humans comprising the steps of:introducing a stentdelivery system into a vessel, the stent delivery system comprising atleast one endovascular support device mounted on a balloon of a ballooncatheter, the at least one endovasular support device anchored to theballoon by encapsulation of the at least one endovascular support deviceby the balloon; advancing the stent delivery system to an area to betreated within the vessels; inflating the balloon of the ballooncatheter to expand the at least one encapsulated endovascular supportdevice within the area to be treated; and deflating the balloon of theballoon catheter so that the balloon pulls away from the at least oneendovascular support device.